Very few engines have an optional reverse crank (I think Fox do one) but with any engine that has a removeable front housing just turn the housing 90 degrees in the normal direction of rotation so the carb's sticking out the same side as the muffler. The beauty of this arrangement is that you can use any of the normal props instead of being limited to the harder to find pusher props. Just remember to put the prop on "backwards"

Another thing to be aware of is that when running on the ground there's not too much cooling air flow so keep full throttle running to a minimum. And don't ever use a plain bearing engine as a pusher...